Fleas, which belong to the insect order Siphonaptera, are obligate ectoparasites for a wide variety of animals, including birds and mammals. Flea infestation of animals is of health and economic concern because fleas are known to cause and/or transmit a variety of diseases. Fleas cause and/or carry infectious agents that cause, for example, flea allergy dermatitis, anemia, murine typhus, plague and tapeworm. In addition, fleas are a problem for animals maintained as pets because the infestation becomes a source of annoyance for the pet owner who may find his or her home generally contaminated with fleas which feed on the pets. As such, fleas are a problem not only when they are on an animal but also when they are in the general environment of the animal.
The medical and veterinary importance of flea infestation has prompted the development of reagents capable of controlling flea infestation. Commonly encountered methods to control flea infestation are generally focused on use of insecticides in formulations such as sprays, shampoos, dusts, dips, or foams, or in pet collars. While some of these products are efficacious, most, at best, offer protection of a very limited duration. Furthermore, many of the methods are often not successful in reducing flea populations on the pet for one or more of the following reasons: (1) failure of owner compliance (frequent administration is required); (2) behavioral or physiological intolerance of the pet to the pesticide product or means of administration; and (3) the emergence of flea populations resistant to the prescribed dose of pesticide. Additional anti-flea products include nontoxic reagents such as insect growth regulators (IGRs), including methoprene, which mimics flea hormones and affect flea larval development.
An alternative method for controlling flea infestation is the use of flea vaccines to be administered to animals prior to or during flea infestation. However, despite considerable interest in developing anti-flea reagents, no flea vaccine presently exists.